The present invention is directed to a control system for a work machine. More particularly, the present invention is directed to a system and method for controlling a work implement to improve the cycle time of a work machine.
Work machines are commonly used to move large amounts of earth or other material in an excavation or dredging operation. These work machines typically include a work implement that is designed to pick up a load of earth or other material from one location and drop off the load at a second location. For example, an excavator may include a work implement that has a ground engaging tool, such as a bucket or a clamshell. An operator may control the motion of the ground engaging tool to pick up a load of earth from an excavation site. The operator may then move the ground engaging tool to a dumping location, where the load of earth may be unloaded to a removal vehicle.
These work machines are commonly powered by hydraulic systems, which may use pressurized fluid to both move the work implements and to move the machine. The hydraulic systems typically include a series of hydraulic actuators, such as, for example, hydraulic cylinders or fluid motors. The movement of these hydraulic actuators may be controlled by controlling the rate and direction of fluid flow into and out of the hydraulic actuator. Typically, a series of hydraulic actuators are distributed throughout the work machine to transmit the power required to move the work machine and the work implement. By controlling the rate and direction of fluid flow into the hydraulic actuators, the movement of the work machine and of the work implement may be controlled.
During an excavation or dredging type operation, an operator will often guide the work machine through a repetitive sequence of steps. For example, in an excavation operation, an operator of a work machine will move the ground engaging tool to a loading, location where the ground engaging tool picks up a load of earth. The operator will then lift the ground engaging tool and move it to a dumping location where the load is unloaded to a removal vehicle. The operator will then return the ground engaging tool to the loading location to pick up a new load of earth. The time taken to complete this sequence of steps may be referred to as the cycle time for the particular operation.
One measure of the efficiency of the work machine may be defined by the amount of material moved during a given period time. Any reduction in the amount of time required to complete a cycle will likely result in an increase in the amount of material moved during a period of time. Thus, a reduction in cycle time may result in an increase in the efficiency of the work machine.
As described in U.S. Pat. No. 5,446,980, one approach to improving the efficiency of a work machine is to automate control of the work implement. In this approach, an automated control system governs the movement of the work implement to perform a particular task with minimal input from an operator. This type of automated control may improve the efficiency of the work machine as the automated control may remain consistently productive, regardless of prolonged hours and environmental considerations.
However, these types of automated control systems do not directly address the issue of reducing cycle time. The automated control systems are typically programmed to guide a work machine through a work cycle in the same way an operator would. Consider, for example, an excavation operation where the work machine has to move the ground engaging tool through a large rotation to move from a loading location to a dumping location. Typically, an operator or an automated control system will move the ground engaging tool from the loading location to the dumping location by actuating a swing assembly on the work machine to pivot the ground engaging tool. The pivoting motion results in the ground engaging tool moving along an arcuate path between the loading and dumping locations. The operator or automated control system will then return the ground engaging tool to the loading location through a similar arcuate pattern. However, these arcuate paths will not typically represent the shortest possible path between the two locations. By moving the ground engaging tool along these arcuate paths, the work machine expends more time than necessary to complete a work cycle, which may result in a decreased efficiency.
The control system of the present invention solves one or more of the problems set forth above.
One aspect of the present invention is directed to a method for controlling a work implement having a ground engaging tool. A swing command is supplied to a swing assembly to move the ground engaging tool about a vertical axis. A crowd command is determined based on the velocity of the swing assembly. The crowd command is calculated to generate a resulting net movement of the ground engaging tool toward a predetermined end point. The crowd command is supplied to a crowd mechanism to move the ground engaging tool towards the predetermined end point.
In another aspect, the present invention is directed to a control system for a work implement having a ground engaging tool. The control system includes a memory configured to store a location of a predetermined end point. A position sensing system is operatively connected to the work implement and is configured to provide an indication of a current position of the ground engaging tool. A control is configured to determine a travel path having a horizontal component path connects the current position of the ground engaging tool with the predetermined end point. At least a portion of the horizontal component of the travel path substantially coincides with a straight line connecting the current position of the ground engaging tool with the predetermined end point. The control is further configured to control the movement of the ground engaging tool to move the ground engaging tool along the travel path to the predetermined end point.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed.